Fix clientTtl cleanup race in Agent

lib/dispatcher/agent.js

@@ -92,7 +92,9 @@ class Agent extends DispatcherBase {
           if (connected) result.count -= 1
           if (result.count <= 0) {
             this[kClients].delete(key)
-            result.dispatcher.close()
+            if (!result.dispatcher.destroyed) {
+              result.dispatcher.close()
+            }
           }
           this[kOrigins].delete(key)
         }

lib/dispatcher/pool-base.js

@@ -48,9 +48,12 @@ class PoolBase extends DispatcherBase {
     }
 
     if (this[kClosedResolve] && queue.isEmpty()) {
-      const closeAll = new Array(this[kClients].length)
+      const closeAll = []
       for (let i = 0; i < this[kClients].length; i++) {
-        closeAll[i] = this[kClients][i].close()
+        const client = this[kClients][i]
+        if (!client.destroyed) {
+          closeAll.push(client.close())
+        }
       }
       return Promise.all(closeAll)
         .then(this[kClosedResolve])
@@ -119,9 +122,12 @@ class PoolBase extends DispatcherBase {
 
   [kClose] () {
     if (this[kQueue].isEmpty()) {
-      const closeAll = new Array(this[kClients].length)
+      const closeAll = []
       for (let i = 0; i < this[kClients].length; i++) {
-        closeAll[i] = this[kClients][i].close()
+        const client = this[kClients][i]
+        if (!client.destroyed) {
+          closeAll.push(client.close())
+        }
       }
       return Promise.all(closeAll)
     } else {

test/issue-4806.js

@@ -0,0 +1,44 @@
+'use strict'
+
+const { test, after } = require('node:test')
+const { createServer } = require('node:http')
+const { once } = require('node:events')
+const { tspl } = require('@matteo.collina/tspl')
+
+const { Agent, request } = require('..')
+
+// https://github.com/nodejs/undici/issues/4806
+test('Agent clientTtl cleanup does not trigger unhandled rejections', async (t) => {
+  t = tspl(t, { plan: 2 })
+
+  const server = createServer((req, res) => {
+    res.end('ok')
+  })
+
+  after(() => server.close())
+
+  server.listen(0, async () => {
+    const agent = new Agent({ clientTtl: 10 })
+    after(async () => agent.close())
+
+    const onUnhandled = (err) => t.fail(err)
+    process.once('unhandledRejection', onUnhandled)
+    after(() => process.removeListener('unhandledRejection', onUnhandled))
+
+    const origin = `http://localhost:${server.address().port}`
+
+    const res1 = await request(origin, { dispatcher: agent })
+    t.strictEqual(res1.statusCode, 200)
+
+    await new Promise(resolve => setTimeout(resolve, 20))
+
+    const res2 = await request(origin, { dispatcher: agent })
+    t.strictEqual(res2.statusCode, 200)
+    res2.body.resume()
+    await once(res2.body, 'end')
+
+    await new Promise(resolve => setTimeout(resolve, 20))
+  })
+
+  await t.completed
+})